Method and system for providing a return path for signals generated by legacy terminals in an optical network

ABSTRACT

A return path system includes inserting RF packets between regular upstream data packets, where the data packets are generated by communication devices such as a computer or internet telephone. The RF packets can be derived from analog RF signals that are produced by legacy video service terminals. In this way, the present invention can provide an RF return path for legacy terminals that shares a return path for regular data packets in an optical network architecture.

STATEMENT REGARDING PRIORITY AND RELATED APPLICATIONS

This application is a continuation of and claims priority to applicationSer. No. 10/389,267 filed Mar. 14, 2003 now U.S. Pat. No. 7,190,901,entitled “Method and System for Providing a Return Path for SignalsGenerated by Legacy Terminals in an Optical Network,” the entirecontents of which are incorporated by reference.

TECHNICAL FIELD

The present invention relates to video, voice, and data communications.More particularly, the present invention relates to a fiber-to-the-home(FTTH) system that is capable of propagating RF terminal signals from asubscriber to a data service provider.

BACKGROUND OF THE INVENTION

The increasing reliance on communication networks to transmit morecomplex data, such as voice and video traffic, is causing a very highdemand for bandwidth. To resolve this demand for bandwidth,communications networks are relying upon optical fiber to transmit thiscomplex data. Conventional communication architectures that employcoaxial cables are slowly being replaced with communication networksthat comprise only fiber optic cables. One advantage that optical fibershave over coaxial cables is that a much greater amount of informationcan be carried on an optical fiber.

While the FTTH optical network architecture has been a dream of manydata service providers because of the aforementioned capacity of opticalfibers, implementing the FTTH optical network architecture may encountersome problems associated with legacy systems that are in current use bysubscribers. For example, many subscribers of data service providers useset top terminals (STTs) to receive and transmit information related tovideo services. The conventional set top terminals are coupled to acoaxial cable. The coaxial cable, in turn, is then connected to fiberoptic cables in a hybrid fiber-coax (HFC) system. The coaxial cable fromthe set top terminals in combination with the fiber optic cables providea two way communication path between the set top terminal and the dataservice hub for purposes such as authorizing a subscriber to viewcertain programs and channels.

For example, conventional set top terminals coupled to coaxial cablesmay provide impulse pay-per-view services. Impulse pay-per-view servicestypically require two way communications between the set top terminaland the data service provider. Another exemplary service that mayrequire two-way communication passed between the set top terminal andthe data service provider is video-on-demand (VOD) services.

For video on demand services, a subscriber can request a program of hischoosing to be played at a selected time from a central video fileserver at the data service hub. The subscriber's VOD program request istransmitted upstream on a return channel that comprises coaxial cablescoupled to fiber optic cables. With the VOD service, a subscribertypically expects VCR-like control for these programs which includes theability to “stop” and “play” the selected program as well as “rewind”and “fast forward” the program.

In conventional HFC systems, a return RF path from the subscriber to thedata service hub is provided. The RF return path is needed because aconventional set top terminal usually modulates its video serviceupstream data onto an analog RF carrier. While the video serviceupstream data may be modulated onto an RF carrier, it is recognized thatthe upstream data may be in digital form.

An RF return path typically comprises two-way RF distribution amplifierswith coaxial cables and two-way fiber optic nodes being used tointerface with fiber optic cables. A pair of fiber optic strands can beused to carry the radio frequency signals between the head end and nodein an analog optical format. Each optical cable of the pair of fiberoptic strands carries analog RF signals: one carries analog RF signalsin the downstream direction (toward the subscriber) while the otherfiber optic cable carries analog RF signals in the reverse or upstreamdirection (from the subscriber). In a more recent embodiment, theupstream spectrum (typically 5-42 MHz in North America) is digitized atthe node. The digital signals are transmitted to the headend, where theyare converted back to the analog RF spectrum of 5-42 MHz. This processtypically uses high data rates (at least 1.25 Gb/s) and a fiber orwavelength dedicated to return traffic from one or two nodes.

Unlike HFC systems, conventional FTTH systems typically do not comprisea return RF path from the subscriber to the data service hub becausemost of the return paths comprise only fiber optic cables that propagatedigital data signals as opposed to analog RF signals. In conventionalFTTH systems, a downstream RF path is usually provided because it isneeded for the delivery of television programs that use conventionalbroadcast signals. This downstream RF path can support RF modulatedanalog and digital signals as well as RF modulated control signals forany set top terminals that may be used by the subscriber. However, asnoted above, conventional FTTH systems do not provide for any capabilityof supporting a return RF path for RF analog signals generated by thelegacy set top terminal.

Accordingly, there is a need in the art for the system and method forcommunicating optical signals between a data service provider and asubscriber that eliminates the use of the coaxial cables and the relatedhardware and software necessary to support the data signals propagatingalong the coaxial cables. There is also a need in the art for a systemand method that provides a return path for RF signals that are generatedby legacy video service terminals. An additional need exists in the artfor a method and system for propagating upstream RF packets with verylow latency and jitter. A further need exists in the art for a method insystem for communicating optical signals between a data service providerand a subscriber that can support either a query-response protocol or acontention protocol. Another need exists in the art for supportinglegacy video service controllers and terminals with an all opticalnetwork architecture.

SUMMARY OF THE INVENTION

The present invention is generally drawn to a system and method forefficient propagation of data and broadcast signals over an opticalfiber network. More specifically, the present invention is generallydrawn to an optical network architecture that can provide a return pathfor RF signals that are generated by existing legacy video serviceterminals. Video service terminals can comprise set top terminals orother like communication devices that may employ RF carriers to transmitupstream information.

In one exemplary embodiment, a portion of the return path may be housedin a subscriber optical interface. The subscriber optical interface maycomprise an analog to digital converter where analog RF electricalsignals produced by a video service terminal are converted to digitalelectrical signals.

The return path in the subscriber optical interface may further comprisea data scaler that shortens or reduces the size of the digitized RFelectrical signals. A data conditioner can be coupled to the datareducer for generating identification information that is linked to thedigitized and reduced RF signals to form RF packets. That is, an RFpacket can comprise digitized and reduced RF signals that are coupledwith identification information generated by the data conditioner.According to a preferred and an exemplary embodiment, the RF packets areformatted as Ethernet packets. However, other packet formats are notbeyond the scope and spirit of the present invention.

The data conditioner may further comprise a buffer such as a FIFO forspeeding up the transmission rate of the RF packets. This increase intransmission rate of the RF packets is an important feature of thepresent invention. A switch connected to the data conditioner andprocessor can be controlled by the processor of the subscriber opticalinterface. The switch may be activated at appropriate times to combinethe RF packets with data signals destined for a data service hub.

More specifically, the RF packets may be inserted between upstreampackets comprising data generated by a subscriber with a communicationdevice such as a computer or internet telephone. The term “upstream” candefine a communication direction where a subscriber originates a datasignal that is sent upwards towards a data service hub of an opticalnetwork. Conversely, the term “downstream” can define a communicationdirection where a data service hub originates a data signal that is sentdownwards towards subscribers of an optical network.

The present invention can provide an RF return path for legacy videoservice terminals that use either a query-response protocol or acontention protocol. In other words, the present invention can supportvideo service terminals in which the timing of upstream RF signals tothe video service controllers is not critical, such as in the DigitalVideo Services (DVS) Standard 178. In the query-response protocol, thedata service hub or headend communicates with a particular subscriberoptical interface that has a set top terminal and waits for a responsefrom the set top terminal. In the contention protocol, a set topterminal wanting to send data to the data service hub contends with allset top terminals for the right to send its information. When a set topterminal is successful, the data service hub acknowledges the set topterminal's request and the set top terminal can then transmit itsinformation to the data service hub. This type of protocol is oftenreferred to as the aloha protocol.

In one exemplary embodiment of the present invention, the subscriberoptical interface converts upstream analog RF signals from the set topterminal into digitized RF Signals. First, the analog signals from thelegacy terminal are filtered with a low pass filter that can part of adiplexer. Then the RF signals are converted into digital signals. Thedigital signals can be split into two data streams. A first data streamcan be mixed down to a zero frequency.

This mixing process can be driven by a local oscillator which can befrequency controlled from a phase locked loop (PLL). The frequency ofthe PLL can be determined by measuring the frequency of the RF signalpassing out of the low pass filter. The local oscillator can be set tothis measured frequency. The measured frequency can be calculated bymeasuring the time between a plurality of zero crossings of thedigitized RF signal.

A second data stream can be mixed with the carrier signal that is at thesame frequency as the first carrier or local oscillator signal, butphased ninety degrees apart from the first oscillator signal. The firstand second data streams can then be scaled down in order to reduce theamount of digitized RF data transmitted. The first and second datastreams can then be multiplexed into a single upstream digital signalthat is propagated to a laser transceiver node and later to a dataservice hub.

In another exemplary embodiment of the present invention, the subscriberoptical interface can determine a control word for a phase locked loop.The control word is loaded into the phase lock loop to establish afrequency of an oscillator. In this embodiment, the local oscillatorfrequency can be determined by measuring the frequency of the incomingRF signal flowing out of the law pass filter. The measured frequency canbe calculated by measuring the time between a plurality of zerocrossings of the RF signal. Once the measured frequency is determined,then an offset frequency can be added to the measured frequency suchthat the RF signal has side bands that extend near, but do not cross, azero frequency value. The analog signal from the local oscillator ismixed with the analog RF return signal generated by a set top terminalto produce a difference frequency. The difference frequency is convertedto the digital domain. The digital signals are then scaled down toreduce the amount of RF data transmitted and the scaled or reduceddigital signals are then transmitted upstream to the laser transceivernode, and later to the data service hub.

A data service hub may comprise another portion of the RF return path.The RF packets bearing the digitized RF signal can then be convertedback to the electrical domain with an optical receiver, along with allother non-RF return data present in the packets. The RF return packetsmay be separated from other upstream packets by either a lasertransceiver node routing device or an internet router, depending how thedata service hub is configured. The RF packet may then be expanded witha data to RF converter that transforms the RF packet back to itsoriginal analog RF signal format. An RF receiver coupled to a videoservice controller may then process the restored analog RF signals.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional block diagram of some core components of anexemplary optical network architecture according to an exemplaryembodiment of the present convention that can support legacy videoservices.

FIG. 2 is a functional block diagram illustrating additional aspects ofan exemplary optical network architecture according to an exemplaryembodiment of the present invention.

FIG. 3 is a functional block diagram illustrating an exemplary dataservice hub according to an exemplary embodiment of the presentinvention.

FIG. 4 is a functional block diagram illustrating an exemplarytransceiver node according to an exemplary embodiment of the presentinvention.

FIG. 5 is a functional block diagram illustrating an optical tap coupledto a plurality of subscriber optical interfaces according to anexemplary embodiment of the present invention.

FIG. 6 is a functional block diagram illustrating a subscriber opticalinterface of one preferred exemplary embodiment that divides upstream RFsignals into two data streams.

FIG. 7 is a functional block diagram illustrating a subscriber opticalinterface of an alternate embodiment that employs a single data streamand a phase locked loop.

FIG. 8 is a graph illustrating a frequency plan for a subscriber opticalinterface according to one exemplary embodiment of the presentinvention.

FIG. 9 is a functional block diagram illustrating some components ofdata-to-RF conversion block according to one preferred exemplaryembodiment of the present invention.

FIG. 10A is a functional block diagram illustrating some components ofdata-to-RF conversion block according to an alternate exemplaryembodiment of the present invention.

FIG. 10B is a graph illustrating a frequency plan for a data service hubaccording to one exemplary embodiment of the present invention.

FIG. 11 is a functional block illustrating exemplary components ofanother subscriber optical interface according to an alternate exemplaryembodiment of the present invention that can accommodate two RF returnfrequencies.

FIG. 12 is a logic flow diagram illustrating an exemplary method forpropagating upstream RF signals towards a data service hub.

FIG. 13 is a logic flow diagram corresponding to the hardware of FIG. 6and exemplary submethod of FIG. 12 for reducing the size of the upstreamRF signals and converting the analog RF signals to digital data packetsaccording to one exemplary embodiment of the present invention.

FIG. 14 is a logic flow diagram corresponding to the hardware of FIG. 7and exemplary submethod of FIG. 12 for reducing the size of the upstreamRF signals and converting the analog RF signals to digital data packetsaccording to one exemplary embodiment of the present invention.

FIG. 15 is a logic flow diagram illustrating an exemplary submethod ofFIGS. 13 and 14 for scaling data received from a video service terminalthat can be performed by a data scaler as illustrated in FIGS. 8 and 9.

FIG. 16 is a logic flow diagram illustrating an exemplary subprocess ofFIG. 12 for combining reduced RF packets with regular data packets.

FIG. 17 is a logic flow diagram illustrating a preferred exemplarysubprocess of FIG. 12 for converting reduced RF data packets intooriginal analog signals according to one exemplary embodiment of thepresent invention.

FIG. 18 is a logic flow diagram illustrating an alternate exemplarysubprocess of FIG. 12 for converting reduced RF data packets intooriginal analog signals according to one exemplary embodiment of thepresent invention.

FIG. 19 illustrates an exemplary scaling restoration process accordingto one exemplary embodiment of the present invention.

FIG. 20 is a logic flow diagram illustrating multiplexing to accommodatemultiple RF return frequencies according to one alternate exemplaryembodiment of the present invention.

FIG. 21 is a logic flow diagram illustrating the exemplary processing ofdownstream video service control signals according to an exemplaryembodiment of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION

The present invention may be embodied in hardware or software or acombination thereof disposed within an optical network. In one exemplaryembodiment, the present invention provides a method for inserting RFpackets between upstream packets comprising data generated by asubscriber with a communication device such as a computer or internettelephone. In this way, the present invention can provide an RF returnpath for legacy video service terminals that shares a return path forregular data packets in an optical network architecture. Video serviceterminals can comprise set top terminals or other like communicationdevices that may employ RF carriers to transmit upstream information.

Referring now to the drawings, in which like numerals represent likeelements throughout the several Figures, aspects of the presentinvention and the illustrative operating environment will be described.

FIG. 1 is a functional block diagram illustrating an exemplary opticalnetwork architecture 100 according to the present invention. Theexemplary optical network architecture 100 comprises a data service hub110 that houses a legacy video services controller 115. The legacy videoservices controller 115 is typically designed to transmit and receivedigital radio-frequency (RF) signals. The legacy video servicescontroller 115 can comprise conventional hardware that supports servicessuch as impulse-pay-per-view and video-on-demand. However, the videoservices controller 115 is not limited to the aforementionedapplications and can include other applications that are not beyond thescope and spirit of the present invention. In some exemplaryembodiments, the video services controller can be split between twolocations. For example, a portion, primarily a computer, can be locatedin a first data service hub 110 that services a plurality of second dataservice hubs 110, while an RF transmitter plus one or more receivers canbe located in each second data service hub 110. The first and pluralityof second data service hubs 110 can be linked using any of several knowncommunications paths and protocols.

The data service hub 110 is connected to a plurality of outdoor lasertransceiver nodes 120. The laser transceiver nodes 120, in turn, areeach connected to a plurality of optical taps 130. The optical taps 130can be connected to a plurality of subscriber optical interfaces 140.Connected to each subscriber optical interface 140 can be video servicesterminal (VST) 117. The video services RF terminal 117 is designed towork with the video services controller 115. The video services RFterminal 117 can receive control signals from the video servicescontroller 115 and can transmit RF-modulated digital signals back to thevideo services controller 115. The RF-modulated digital signals maycomprise the options selected by a user. However, the signals producedby the video service terminal 117 could be analog in form and thenmodulated onto the RF carrier. But most legacy video service terminals117 as of the writing of this description produce digital signals thatare modulated onto an analog RF carrier.

The video services terminal 117 can permit a subscriber to selectoptions that are part of various exemplary video services such asimpulse-pay-per-view and video-on-demand. However, as noted above withrespect to the video services controller 115, the present invention isnot limited to the aforementioned applications and can include numerousother applications where RF analog signals are used to carry informationback to the video services controller 115.

Between respective components of the exemplary optical networkarchitecture 100 are optical waveguides such as optical waveguides 150,160, 170, and 180. The optical waveguides 150-180 are illustrated byarrows where the arrowheads of the arrows illustrate exemplarydirections of data flow between respective components of theillustrative and exemplary optical network architecture 100. While onlyan individual laser transceiver node 120, an individual optical tap 130,and an individual subscriber optical interface 140 are illustrated inFIG. 1, as will become apparent from FIG. 2 and its correspondingdescription, a plurality of laser transceiver nodes 120, optical taps130, and subscriber optical interfaces 140 can be employed withoutdeparting from the scope and spirit of the present invention. Typically,in many of the exemplary embodiments of the RF return system of thepresent invention, multiple subscriber optical interfaces 140 areconnected to one or more optical taps 130.

The outdoor laser transceiver node 120 can allocate additional orreduced bandwidth based upon the demand of one or more subscribers thatuse the subscriber optical interfaces 140. The outdoor laser transceivernode 120 can be designed to withstand outdoor environmental conditionsand can be designed to hang on a strand or fit in a pedestal or “hardhole.” The outdoor laser transceiver node can operate in a temperaturerange between minus 40 degrees Celsius to plus 60 degrees Celsius. Thelaser transceiver node 120 can operate in this temperature range byusing passive cooling devices that do not consume power.

Unlike the conventional routers disposed between the subscriber opticalinterface 140 and data service hub 110, the outdoor laser transceivernode 120 does not require active cooling and heating devices thatcontrol the temperature surrounding the laser transceiver node 120. TheRF system of the present invention attempts to place more of thedecision-making electronics at the data service hub 110 instead of thelaser transceiver node 120. Typically, the decision-making electronicsare larger in size and produce more heat than the electronics placed inthe laser transceiver node of the present invention. Because the lasertransceiver node 120 does not require active temperature controllingdevices, the laser transceiver node 120 lends itself to a compactelectronic packaging volume that is typically smaller than theenvironmental enclosures of conventional routers. Further details of thecomponents that make up the laser transceiver node 120 will be discussedin further detail below with respect to FIGS. 5, 6, and 7.

In one exemplary embodiment of the present invention, three trunkoptical waveguides 160, 170, and 180 (that can comprise optical fibers)can propagate optical signals from the data service hub 10 to theoutdoor laser transceiver node 120. It is noted that the term “opticalwaveguide” used in the present application can apply to optical fibers,planar light guide circuits, and fiber optic pigtails and other likeoptical waveguide components that are used to form an opticalarchitecture.

A first optical waveguide 160 can carry downstream broadcast video andcontrol signals generated by the video services controller 115. Thesignals can be carried in a traditional cable television format whereinthe broadcast signals are modulated onto carriers, which in turn,modulate an optical transmitter (not shown in this Figure) in the dataservice hub 110. The first optical waveguide 160 can also carry upstreamRF signals that are generated by respective video service terminals 117.Further details of the format of the upstream RF signals will bediscussed below.

A second optical waveguide 170 can carry upstream and downstreamtargeted services such as data and telephone services to be delivered toor received from one or more subscriber optical interfaces 140. Inaddition to carrying subscriber-specific optical signals, the secondoptical waveguide 170 can also propagate internet protocol broadcastpackets, as is understood by those skilled in the art.

In one exemplary embodiment, a third optical waveguide 180 can transportdata signals upstream from the outdoor laser transceiver node 120 to thedata service hub 110. The optical signals propagated along the thirdoptical waveguide 180 can also comprise data and telephone servicesreceived from one or more subscribers. Similar to the second opticalwaveguide 170, the third optical waveguide 180 can also carry IPbroadcast packets, as is understood by those skilled in the art.

The third or upstream optical waveguide 180 is illustrated with dashedlines to indicate that it is merely an option or part of one exemplaryembodiment according to the present invention. In other words, the thirdoptical waveguide 180 can be removed. In another exemplary embodiment,the second optical waveguide 170 propagates optical signals in both theupstream and downstream directions as is illustrated by the doublearrows depicting the second optical waveguide 170.

In such an exemplary embodiment where the second optical waveguide 170propagates bidirectional optical signals, only two optical waveguides160, 170 would be needed to support the optical signals propagatingbetween the data server's hub 110 in the outdoor laser transceiver node120. In another exemplary embodiment (not shown), a single opticalwaveguide can be the only link between the data service hub 110 and thelaser transceiver node 120. In such a single optical waveguideembodiment, three different wavelengths can be used for the upstream anddownstream signals. Alternatively, bi-directional data could bemodulated on one wavelength.

In one exemplary embodiment, the optical tap 130 can comprise an 8-wayoptical splitter. This means that the optical tap 130 comprising an8-way optical splitter can divide downstream optical signals eight waysto serve eight different subscriber optical interfaces 140. In theupstream direction, the optical tap 130 can combine the optical signalsreceived from the eight subscriber optical interfaces 140.

In another exemplary embodiment, the optical tap 130 can comprise a4-way splitter to service four subscriber optical interfaces 140. Yet inanother exemplary embodiment, the optical tap 130 can further comprise a4-way splitter that is also a pass-through tap meaning that a portion ofthe optical signal received at the optical tap 130 can be extracted toserve the 4-way splitter contained therein while the remaining opticalenergy is propagated further downstream to another optical tap oranother subscriber optical interface 140. The present invention is notlimited to 4-way and 8-way optical splitters. Other optical taps havingfewer or more than 4-way or 8-way splits are not beyond the scope of thepresent invention.

Referring now to FIG. 2, this Figure is a functional block diagramillustrating an exemplary optical network architecture 100 that furtherincludes subscriber groupings 200 that correspond with a respectiveoutdoor laser transceiver node 120. FIG. 2 illustrates the diversity ofthe exemplary optical network architecture 100 where a number of opticalwaveguides 150 connected between the outdoor laser transceiver node 120and the optical taps 130 is minimized. FIG. 2 also illustrates thediversity of subscriber groupings 200 that can be achieved with theoptical tap 130.

Each optical tap 130 can comprise an optical splitter. The optical tap130 allows multiple subscriber optical interfaces 140 to be coupled to asingle optical waveguide 150 that is connected to the outdoor lasertransceiver node 120. In one exemplary embodiment, six optical fibers150 are designed to be connected to the outdoor laser transceiver node120. Through the use of the optical taps 130, sixteen subscribers can beassigned to each of the six optical fibers 150 that are connected to theoutdoor laser transceiver node 120.

In another exemplary embodiment, twelve optical fibers 150 can beconnected to the outdoor laser transceiver node 120 while eightsubscriber optical interfaces 140 are assigned to each of the twelveoptical fibers 150. Those skilled in the art will appreciate that thenumber of subscriber optical interfaces 140 assigned to a particularwaveguide 150 that is connected between the outdoor laser transceivernode 120 and a subscriber optical interface 140 (by way of the opticaltap 130) can be varied or changed without departing from the scope andspirit of the present invention. Further, those skilled in the artrecognize that the actual number of subscriber optical interfaces 140assigned to the particular fiber optic cable is dependent upon theamount of power available on a particular optical fiber 150.

As depicted in subscriber grouping 200, many configurations forsupplying communication services to subscribers are possible. Forexample, while optical tap 130 _(A) can connect subscriber opticalinterfaces 140 _(A1) through subscriber optical interface 140 _(AN) tothe outdoor laser transmitter node 120, optical tap 130 _(A) can alsoconnect other optical taps 130 such as optical tap 130 _(AN) to thelaser transceiver node 120. The combinations of optical taps 130 withother optical taps 130 in addition to combinations of optical taps 130with subscriber optical interfaces 140 are limitless. With the opticaltaps 130, concentrations of distribution optical waveguides 150 at thelaser transceiver node 120 can be reduced. Additionally, the totalamount of fiber needed to service a subscriber grouping 200 can also bereduced.

With the active laser transceiver node 120 of the present invention, thedistance between the laser transceiver node 120 and the data service hub110 can comprise a range between 0 and 80 kilometers. However, thepresent invention is not limited to this range. Those skilled in the artwill appreciate that this range can be expanded by selecting variousoff-the-shelf components that make up several of the devices of thepresent system.

Those skilled in the art will appreciate that other configurations ofthe optical waveguides disposed between the data service hub 110 andoutdoor laser transceiver node 120 are not beyond the scope of thepresent invention. Because of the bi-directional capability of opticalwaveguides, variations in the number and directional flow of the opticalwaveguides disposed between the data service hub 110 and the outdoorlaser transceiver node 120 can be made without departing from the scopeand spirit of the present invention.

Referring now to FIG. 3, this functional block diagram illustrates anexemplary data service hub 110 of the present invention. The exemplarydata service hub 110 illustrated in FIG. 3 is designed for a two trunkoptical waveguide system. That is, this data service hub 110 of FIG. 3is designed to send and receive optical signals to and from the outdoorlaser transceiver node 120 along the first optical waveguide 160 and thesecond optical waveguide 170. With this exemplary embodiment, both thefirst optical waveguide 160 and the second optical waveguide 170 supportbi-directional data flow. In this way, the third optical waveguide 180discussed above is not needed.

The data service hub 110 can comprise one or more modulators 310, 315that are designed to support television broadcast services. The one ormore modulators 310, 315 can be analog or digital type modulators. Inone exemplary embodiment, there can be at least 78 modulators present inthe data service hub 110. Those skilled in the art will appreciate thatthe number of modulators 310, 315 can be varied without departing fromthe scope and spirit of the present invention.

The signals from the modulators 310, 315 are combined in a firstcombiner 320A. The control signals from the video services controller115 are modulated on an RF carrier by an RF transmitter 303. The RFtransmitter 303 feeds its downstream analog RF electrical signals into asecond combiner 320B where the electrical signals from the twomodulators 310, 315 are combined. The combined video services controllersignals and broadcast video signals are supplied to an opticaltransmitter 325 where these signals are converted into optical form.

Those skilled in the art will recognize that a number of variations ofthis signal flow are possible without departing from the scope andspirit of the present invention. For example, the two combiners 320A and320B may actually be one and the same combiner. Also, video signals maybe generated at another data service hub 110 and sent to the dataservice hub 110 of FIG. 3 using any of a plurality of differenttransmission methods known to these skilled in the art. For example,some portion of the video signals may be generated and converted tooptical form at a remote first data service hub 110. At a second dataservice hub 110, they may be combined with other signals generatedlocally.

The optical transmitter 325 can comprise one of Fabry-Perot (F-P) LaserTransmitters, distributed feedback lasers (DFBs), or Vertical CavitySurface Emitting Lasers (VCSELs). However, other types of opticaltransmitters are possible and are not beyond the scope of the presentinvention. With the aforementioned optical transmitters 325, the dataservice hub 110 lends itself to efficient upgrading by usingoff-the-shelf hardware to generate optical signals.

The optical signals generated by the optical transmitter 325 arepropagated to amplifier 330 such as an Erbium Doped Fiber Amplifier(EDFA) where the optical signals are amplified. The amplified opticalsignals are then propagated out of the data service hub 110 via abi-directional video signal input/output port 335 which is connected toone or more first optical waveguides 160.

The bi-directional video signal input/output port 335 is connected toone or more first optical waveguides 160 that support bi-directionaloptical signals originating from the data service hub 110 and videoservices terminals 117.

The data-to-RF converter 307 that transforms RF packets back into theiroriginal RF analog electrical format. Further details of RF converter307 will be discussed below with respect to FIGS. 9-10 and 17-18. The RFanalog electrical signals generated by the data-to-RF converter 307 aredemodulated by an RF receiver 309. The demodulated signals are thenpropagated to the video services controller 115.

The data service hub 110 illustrated in FIG. 3 can further comprise anInternet router 340. According to one and preferred exemplaryembodiment, the internet router 340 can separate RF return packets fromother data packets and send them to the data to RF converter 307. Thedata service hub 110 can further comprise a telephone switch 345 thatsupports telephony service to the subscribers of the optical networksystem 100. However, other telephony service such as Internet Protocoltelephony can be supported by the data service hub 110. If only InternetProtocol telephony is supported by the data service hub 110, then it isapparent to those skilled in the art that the telephone switch 345 couldbe eliminated in favor of lower cost VoIP equipment. For example, inanother exemplary embodiment (not shown), the telephone switch 345 couldbe substituted with other telephone interface devices such as a softswitch and gateway. But if the telephone switch 345 is needed, it may belocated remotely from the data service hub 110 and can be connectedthrough any of several conventional methods of interconnection.

The data service hub 110 can further comprise a logic interface 350 thatis connected to a laser transceiver node routing device 355. The logicinterface 350 can comprise a Voice over Internet Protocol (VoIP) gatewaywhen required to support such a service. The laser transceiver noderouting device 355 can comprise a conventional router that supports aninterface protocol for communicating with one or more laser transceivernodes 120. This interface protocol can comprise one of gigabit or fasterEthernet, Internet Protocol (IP) or SONET protocols. However, thepresent invention is not limited to these protocols. Other protocols canbe used without departing from the scope and spirit of the presentinvention.

The logic interface 350 and laser transceiver node routing device 355can read packet headers originating from the laser transceiver nodes 120and the internet router 340. The logic interface 350 can also translateinterfaces with the telephone switch 345. After reading the packetheaders, the logic interface 350 and laser transceiver node routingdevice 355 can determine where to send the packets of information.

Specifically, instead of using the internet router 340 to identify RFpackets and according to an alternate exemplary embodiment, the lasertransceiver node routing device 355 can identify RF packets and separatethem from other data packets. The laser transceiver node routing device355 could then forward RF packets to the data to RF converter 307. Theconnection between the laser transceiver node routing device 355 and thedata to RF converter 307 has been illustrated with dashed lines toindicate that this connection is made as an alternative to theconnection between the internet router 340 and the data to RF converter307.

The laser transceiver node routing device 355 can also supply downstreamdata signals to respective optical transmitters 325. The data signalsconverted by the optical transmitters 325 can then be propagated to abi-directional splitter 360. The optical signals sent from the opticaltransmitter 325 into the bi-directional splitter 360 can then bepropagated towards a bi-directional data input/output port 365 that isconnected to a second optical waveguide 170 that supports bi-directionaloptical data signals between the data service hub 110 and a respectivelaser transceiver node 120.

Upstream optical signals received from a respective laser transceivernode 120 can be fed into the bi-directional data input/output port 365where the optical signals are then forwarded to the bi-directionalsplitter 360. From the bi-directional splitter 360, respective opticalreceivers 370 can convert the upstream optical signals into theelectrical domain. The upstream electrical signals generated byrespective optical receivers 370 are then fed into the laser transceivernode routing device 355. As noted above, each optical receiver 370 cancomprise one or more photoreceptors or photodiodes that convert opticalsignals into electrical signals.

When distances between the data service hub 110 and respective lasertransceiver nodes 120 are modest, the optical transmitters 325 canpropagate optical signals at 1310 nm. But where distances between thedata service hub 110 and the laser transceiver node are more extreme,the optical transmitters 325 can propagate the optical signals atwavelengths of 1550 nm with or without appropriate amplificationdevices.

Those skilled in the art will appreciate that the selection of opticaltransmitters 325 for each circuit may be optimized for the optical pathlengths needed between the data service hub 110 and the outdoor lasertransceiver node 120. Further, those skilled in the art will appreciatethat the wavelengths discussed are practical but are only illustrativein nature. In some scenarios, it may be possible to use communicationwindows at 1310 and 1550 nm in different ways without departing from thescope and spirit of the present invention. Further, the presentinvention is not limited to a 1310 and 1550 nm wavelength regions. Thoseskilled in the art will appreciate that smaller or larger wavelengthsfor the optical signals are not beyond the scope and spirit of thepresent invention.

Referring now to FIG. 4, this Figure illustrates a functional blockdiagram of an exemplary outdoor laser transceiver node 120A of thepresent invention. In this exemplary embodiment, the laser transceivernode 120A can comprise a bi-directional optical signal input port 405that can receive optical signals propagated from the data service hub110 that are propagated along a first optical waveguide 160. The opticalsignals received at the bi-directional optical signal input port 405 cancomprise downstream broadcast video data and downstream video servicecontrol signals.

The downstream optical signals received at the input port 405 arepropagated through a an amplifier 410 such as an Erbium Doped FiberAmplifier (EDFA) in which the optical signals are amplified. Theamplified optical signals are then propagated to an optical splitter 415that divides the downstream broadcast video optical signals and videoservice control signals among diplexers 420 that are designed to forwardoptical signals to predetermined subscriber groups 200.

The laser transceiver node 120 can further comprise a bi-directionaloptical signal input/output port 425 that connects the laser transceivernode 120 to a second optical waveguide 170 that supports bi-directionaldata flow between the data service hub 110 and laser transceiver node120. Downstream optical signals flow through the bi-directional opticalsignal input/output port 425 to an optical waveguide transceiver 430that converts downstream optical signals into the electrical domain. Theoptical waveguide transceiver further converts upstream electricalsignals into the optical domain. The optical waveguide transceiver 430can comprise an optical/electrical converter and an electrical/opticalconverter.

Downstream and upstream electrical signals are communicated between theoptical waveguide transceiver 430 and an optical tap routing device 435.The optical tap routing device 435 can manage the interface with thedata service hub optical signals and can route or divide or apportionthe data service hub signals according to individual tap multiplexers440 that communicate optical signals with one or more optical taps 130and ultimately one or more subscriber optical interfaces 140. It isnoted that tap multiplexers 440 operate in the electrical domain tomodulate laser transmitters in order to generate optical signals thatare assigned to groups of subscribers coupled to one or more opticaltaps.

Optical tap routing device 435 is notified of available upstream datapackets and upstream RF packets as they arrive, by each tap multiplexer440. The optical tap routing device is connected to each tap multiplexer440 to receive these upstream data and RF packets. The optical taprouting device 435 relays the RF packets and information packets thatcan comprise data and/or telephony packets to the data service hub 110via the optical waveguide transceiver 430 and bi-directional opticalsignal input/output 425. The optical tap routing device 435 can build alookup table from these upstream data packets coming to it from all tapmultiplexers 440 (or ports), by reading the source IP address of eachpacket, and associating it with the tap multiplexer 440 through which itcame.

The aforementioned lookup table can be used to route packets in thedownstream path. As each downstream data packet comes in from theoptical waveguide transceiver 430, the optical tap routing device looksat the destination IP address (which is the same as the source IPaddress for the upstream packets). From the lookup table the optical taprouting device 435 can determine which port (or, tap multiplexer 440) isconnected to that IP address, so it sends the packet to that port. Thiscan be described as a normal layer 3 router function as is understood bythose skilled in the art.

The optical tap routing device 435 can assign multiple subscribers to asingle port. More specifically, the optical tap routing device 435 canservice groups of subscribers with corresponding respective, singleports. The optical taps 130 coupled to respective tap multiplexers 440can supply downstream optical signals to pre-assigned groups ofsubscribers who receive the downstream optical signals with thesubscriber optical interfaces 140.

In other words, the optical tap routing device 435 can determine whichtap multiplexers 440 is to receive a downstream electrical signal, oridentify which tap multiplexer 440 propagated an upstream optical signal(that is received as an electrical signal). The optical tap routingdevice 435 can format data and implement the protocol required to sendand receive data from each individual subscriber connected to arespective optical tap 130. The optical tap routing device 435 cancomprise a computer or a hardwired apparatus that executes a programdefining a protocol for communications with groups of subscribersassigned to individual ports. Exemplary embodiments of programs definingthe protocol is discussed in the following copending and commonlyassigned non-provisional patent applications, the entire contents ofwhich are hereby incorporated by reference: “Method and System forProcessing Downstream Packets of an Optical Network,” filed on Oct. 26,2001 in the name of Stephen A. Thomas et al. and assigned U.S. Ser. No.10/045,652; and “Method and System for Processing Upstream Packets of anOptical Network,” filed on Oct. 26, 2001 in the name of Stephen A.Thomas et al. and assigned U.S. application Ser. No. 10/045,584.

The single ports of the optical tap routing device are connected torespective tap multiplexers 440. With the optical tap routing device435, the laser transceiver node 120 can adjust a subscriber's bandwidthon a subscription basis or on an as-needed or demand basis. The lasertransceiver node 120 via the optical tap routing device 435 can offerdata bandwidth to subscribers in pre-assigned increments. For example,the laser transceiver node 120 via the optical tap routing device 435can offer a particular subscriber or groups of subscribers bandwidth inunits of 1, 2, 5, 10, 20, 50, 100, 200, and 450 Megabits per second(Mb/s). Those skilled in the art will appreciate that other subscriberbandwidth units are not beyond the scope of the present invention.

Electrical signals are communicated between the optical tap routingdevice 435 and respective tap multiplexers 440. The tap multiplexers 440propagate optical signals to and from various groupings of subscribersby way of laser optical transmitter 525 and laser optical receiver 370.Each tap multiplexer 440 is connected to a respective opticaltransmitter 325. As noted above, each optical transmitter 325 cancomprise one of a Fabry-Perot (F-P) laser, a distributed feedback laser(DFB), or a Vertical Cavity Surface Emitting Laser (VCSEL). The opticaltransmitters produce the downstream optical signals that are propagatedtowards the subscriber optical interfaces 140. Each tap multiplexer 440is also coupled to an optical receiver 370. Each optical receiver 370,as noted above, can comprise photoreceptors or photodiodes. Since theoptical transmitters 325 and optical receivers 370 can compriseoff-the-shelf hardware to generate and receive respective opticalsignals, the laser transceiver node 120 lends itself to efficientupgrading and maintenance to provide significantly increased data rates.

Each optical transmitter 325 and each optical receiver 370 are connectedto a respective bi-directional splitter 360. Each bi-directionalsplitter 360 in turn is connected to a diplexer 420 which combines theunidirectional optical signals received from the splitter 415 with thedownstream optical signals received from respective optical receivers370. In this way, broadcast video services as well as data services canbe supplied with a single optical waveguide such as a distributionoptical waveguide 150 as illustrated in FIG. 2. In other words, opticalsignals can be coupled from each respective diplexer 420 to a combinedsignal input/output port 445 that is connected to a respectivedistribution optical waveguide 150.

Unlike the conventional art, the laser transceiver node 120 does notemploy a conventional router. The components of the laser transceivernode 120 can be disposed within a compact electronic packaging volume.For example, the laser transceiver node 120 can be designed to hang on astrand or fit in a pedestal similar to conventional cable TV equipmentthat is placed within the “last,” mile or subscriber proximate portionsof a network. It is noted that the term, “last mile,” is a generic termoften used to describe the last portion of an optical network thatconnects to subscribers.

Also because the optical tap routing device 435 is not a conventionalrouter, it does not require active temperature controlling devices tomaintain the operating environment at a specific temperature. Opticaltap routing device 435 does not need active temperature controllingdevices because it can be designed with all temperature-ratedcomponents. In other words, the laser transceiver node 120 can operatein a temperature range between minus 40 degrees Celsius to 60 degreesCelsius in one exemplary embodiment.

While the laser transceiver node 120 does not comprise activetemperature controlling devices that consume power to maintaintemperature of the laser transceiver node 120 at a single temperature,the laser transceiver node 120 can comprise one or more passivetemperature controlling devices 450 that do not consume power. Thepassive temperature controlling devices 450 can comprise one or moreheat sinks or heat pipes that remove heat from the laser transceivernode 120. Those skilled in the art will appreciate that the presentinvention is not limited to these exemplary passive temperaturecontrolling devices. Further, those skilled in the art will alsoappreciate the present invention is not limited to the exemplaryoperating temperature range disclosed. With appropriate passivetemperature controlling devices 450, the operating temperature range ofthe laser transceiver node 120 can be reduced or expanded.

In addition to the laser transceiver node's 120 ability to withstandharsh outdoor environmental conditions, the laser transceiver node 120can also provide high speed symmetrical data transmissions. In otherwords, the laser transceiver node 120 can propagate the same bit ratesdownstream and upstream to and from a network subscriber. This is yetanother advantage over conventional networks, which typically cannotsupport symmetrical data transmissions as discussed in the backgroundsection above. Further, the laser transceiver node 120 can also serve alarge number of subscribers while reducing the number of connections atboth the data service hub 110 and the laser transceiver node 120 itself.

The laser transceiver node 120 also lends itself to efficient upgradingthat can be performed entirely on the network side or data service hub110 side. That is, upgrades to the hardware forming the lasertransceiver node 120 can take place in locations between and within thedata service hub 110 and the laser transceiver node 120. This means thatthe subscriber side of the network (from distribution optical waveguides150 to the subscriber optical interfaces 140) can be left entirelyin-tact during an upgrade to the laser transceiver node 120 or dataservice hub 110 or both.

The following is provided as an example of an upgrade that can beemployed utilizing the principles of the present invention. In oneexemplary embodiment of the invention, the subscriber side of the lasertransceiver node 120 can service six groups of 16 subscribers each for atotal of up to 96 subscribers. Each group of 16 subscribers can share adata path of about 450 Mb/s speed. Six of these paths represents a totalspeed of 6×450=2.7 Gb/s. In the most basic form, the data communicationspath between the laser transceiver node 120 and the data service hub 110can operate at 1 Gb/s. Thus, while the data path to subscribers cansupport up to 2.7 Gb/s, the data path to the network can only support 1Gb/s. This means that not all of the subscriber bandwidth is useable.This is not normally a problem due to the statistical nature ofbandwidth usage.

An upgrade could be to increase the 1 Gb/s data path speed between thelaser transceiver node 120 and the data service hub 110. This may bedone by adding more 1 Gb/s data paths. Adding one more path wouldincrease the data rate to 2 Gb/s, approaching the total subscriber-sidedata rate. A third data path would allow the network-side data rate toexceed the subscriber-side data rate. In other exemplary embodiments,the data rate on one link could rise from 1 Gb/s to 2 Gb/s then to 10Gb/s, so when this happens, a link can be upgraded without adding moreoptical links.

The additional data paths (bandwidth) may be achieved by any of themethods known to those skilled in the art. It may be accomplished byusing a plurality of optical waveguide transceivers 430 operating over aplurality of optical waveguides, or they can operate over one opticalwaveguide at a plurality of wavelengths, or it may be that higher speedoptical waveguide transceivers 430 could be used as shown above. Thus,by upgrading the laser transceiver node 120 and the data service hub 110to operate with more than a single 1 Gb/s link, a system upgrade iseffected without having to make changes at the subscribers' premises.

Referring now to FIG. 5, this Figure is a functional block diagramillustrating an optical tap 130 connected to a plurality of subscriberoptical interfaces 140 by optical waveguides 150 according to oneexemplary embodiment of the present invention. The optical tap 130 cancomprise a combined signal input/output port 505 that is connected toanother distribution optical waveguide 150 that is connected to a lasertransceiver node 120. As noted above, the optical taps 130 can comprisean optical splitter 510 that can be a 4-way or 8-way optical splitter.Other optical taps having fewer or more than 4-way or 8-way splits arenot beyond the scope of the present invention.

The optical tap 130 can divide downstream optical signals to serverespective subscriber optical interfaces 140. In the exemplaryembodiment in which the optical tap 130 comprises a 4-way optical tap,such an optical tap can be of the pass-through type, meaning that aportion of the downstream optical signals is extracted or divided toserve a 4-way splitter contained therein, while the rest of the opticalenergy is passed further downstream to other distribution opticalwaveguides 150. The optical tap 130 is an efficient coupler that cancommunicate optical signals between the laser transceiver node 120 and arespective subscriber optical interface 140. Optical taps 130 can becascaded, or they can be connected in a star architecture from the lasertransceiver node 120. As discussed above, the optical tap 130 can alsoroute signals to other optical taps that are downstream relative to arespective optical tap 130.

The optical tap 130 can also connect to a limited or small number ofdistribution optical waveguides 150 so that high concentrations ofoptical waveguides are not present at any particular laser transceivernode 120. In other words, in one exemplary embodiment, the optical tapcan connect to a limited number of optical waveguides 150 at a pointremote from the laser transceiver node 120 so that high concentrationsof optical waveguides 150 at a laser transceiver node can be avoided.

However, those skilled in the art will appreciate that the optical tap130 can be incorporated within the laser transceiver node 120 withrespect to another exemplary embodiment (not shown).

The subscriber optical interface 140 functions to convert downstreamoptical signals received from the optical tap 130 into the electricaldomain that can be processed with appropriate communication devices. Thesubscriber optical interface 140 further functions to convert upstreamdata and RF packet electrical signals into upstream optical signals thatcan be propagated along a distribution optical waveguide 150 to theoptical tap 130.

Referring now to FIG. 6, one exemplary embodiment of a first subscriberoptical interface 140A is illustrated. The subscriber optical interface140A can comprise an optical diplexer 515 that divides the downstreamoptical signals received from the distribution optical waveguide 150between a bi-directional optical signal splitter 520 and an analogoptical receiver 525. The optical diplexer 515 can receive upstreamoptical signals generated by a digital optical transmitter 530. Thedigital optical transmitter 530 converts electrical binary/digitalsignals such as upstream data packets and RF packets to optical form sothat the optical signals can be transmitted back to the data service hub110. Conversely, the digital optical receiver 540 converts opticalsignals into electrical binary/digital signals so that the electricaldata signals can be handled by processor 550. Processor 550 can comprisean application specific integrated circuit (ASIC) in combination with acentral processing unit (CPU). However, other hardware or softwareimplementations or combinations thereof are not beyond the scope andspirit of the present invention.

The RF return system of the present invention can propagate the opticalsignals at various wavelengths. However, the wavelength regionsdiscussed are practical and are only illustrative of exemplaryembodiments. Those skilled in the art will appreciate that otherwavelengths that are either higher or lower than or between the 1310 and1550 nm wavelength regions are not beyond the scope of the presentinvention.

The analog optical receiver 525 can convert the downstream broadcastoptical video signals into modulated RF television signals anddownstream video service control signals into analog RF signals that arepropagated through an RF diplexer 507 and out of the modulated RF signalinput/output 535. The modulated RF bi-directional signal input/output535 can feed into the video services terminal 117. The video servicesterminal 117 can be coupled to a tuner 503 that comprises a televisionset or radio. The analog optical receiver 525 can process analogmodulated RF transmission as well as digitally modulated RFtransmissions for digital TV applications.

The bi-directional optical signal splitter 520 can propagate combinedoptical signals in their respective directions. That is, downstreamoptical signals entering the bi-directional optical splitter 520 fromthe optical the optical diplexer 515, are propagated to the digitaloptical receiver 540. Upstream optical signals entering it from thedigital optical transmitter 530 are sent to optical diplexer 515 andthen to optical tap 130. The bi-directional optical signal splitter 520is connected to a digital optical receiver 540 that converts downstreamdata optical signals into the electrical domain. Meanwhile thebi-directional optical signal splitter 520 is also connected to adigital optical transmitter 530 that converts upstream data packet andRF packet electrical signals into the optical domain.

The digital optical receiver 540 can comprise one or more photoreceptorsor photodiodes that convert optical signals into the electrical domain.The digital optical transmitter 530 can comprise one or more lasers suchas the Fabry-Perot (F-P) Lasers, distributed feedback lasers, andVertical Cavity Surface Emitting Lasers (VCSELs). Other types of lasersare within the scope and spirit of the invention.

The digital optical receiver 540 and digital optical transmitter 530 areconnected to a processor 550 that selects data intended for the instantsubscriber optical interface 140 based upon an embedded address. Thedata handled by the processor 550 can comprise one or more of telephonyand data services such as an Internet service. The processor 550 isconnected to a telephone input/output 560 that can comprise an analoginterface. The processor 550 is also connected to a data interface 555that can provide a link to computer devices, ISDN phones, and other likedevices. Alternatively, the data interface 555 can comprise an interfaceto a Voice over Internet Protocol (VoIP) telephone or Ethernettelephone. The data interface 555 can comprise one of Ethernet (10BaseT,100BaseT, Gigabit) interface, HPNA interface, a universal serial bus(USB) an IEEE1394 interface, an ADSL interface, and other likeinterfaces.

The processor 550 is also designed to create the upstream RF packetsthat will transport the RF signals from the video services terminal 117to the data service hub 110. Specifically, the RF signals to be returnedfrom the video service terminal 117 in a subscriber's home arepropagated towards the modulated RF input/output signal interface 535.Each RF return signal can comprise a frequency that exists between anexemplary range of 5 and 42 MHz in North America. The RF signal cancomprise an occasional burst of RF modulated data, which must betransported back to the headend.

When the video services terminal 117 generates RF signals, these RFsignals are propagated through the modulated RF signal input/outputsignal interface 535 to the diplexer 507. The diplexer 507 can comprisea high pass filter 517 and a low pass filter 519. The high pass filtersupports downstream analog RF signals that can comprise video contentand control signals for the video service terminal 117. The low passfilter 519 can support upstream analog RF signals generated by the videoservice terminal 117.

The diplexer 507 passes the upstream analog RF signals to ananalog-to-digital (A/D) converter 509. From the A/D converter 509, thedigital RF signals can be split into two data streams. A first datastream can be mixed down to a zero frequency in a first mixer 528A bymixing the first data stream with a carrier frequency produced by alocal oscillator 526. In other words, this mixing process can be drivenby the local oscillator 526 which can be frequency controlled from aphase locked loop (PLL) 523. The frequency of the PLL 523 can bedetermined by a frequency detector 521 that measures the frequency ofthe RF signal at the A/D converter 509 passing out of the low passfilter. The local oscillator 526 can be set to this measured frequency.The measured frequency can be calculated by measuring the time between aplurality of zero crossings of the digitized RF signal.

A second data stream flowing out of the A/D converter 509 can be mixedin a second mixer 528B with a carrier signal that is at the samefrequency as the first carrier or local oscillator signal, but phasedninety degrees apart from the first carrier signal. This phase shift ofthe first carrier signal can be made with a phase shifter 527. The firstand second data streams flowing through the first and second mixers528A, 528B can be propagated through low pass filters 519A, 519B. Thetwo data streams can then be scaled down with a data scaler 539 in orderto reduce the amount of digitized RF data transmitted. While in the datareducer 539, certain algorithms are applied to reduce the amount of datatransmitted. A number of algorithms related to subsampling and othertechniques are known to those skilled in the art. Further details of thedata scaler 539 will be discussed below with respect to FIG. 15.

The reduced data streams comprising digitized RF signals are thenpropagated to a multiplexer 529 where the two data streams are combinedand then propagated to a data conditioner 407. The data conditioner 407at this stage can speed up data transmission of the RF signals. The dataconditioner 407 can comprise a buffer such as a FIFO that also inputsidentification information with the digitized RF signals to form RFpackets. That is, an RF packet can comprise digitized and reduced RFsignals that are coupled with identification information.

As noted above, the RF packets can be formatted as Ethernet packets.However, other packet formats are not beyond the scope and spirit of thepresent invention. Reduced RF signals may enter the data conditioner 407at an exemplary transmission speed of 40 Megabits per second (Mps) whilethe newly formed RF packets exit the data conditioner 407 at anexemplary transmission speed of 500 Megabits per second (Mps). However,other transmission speeds are not beyond the scope of the presentinvention.

RF packets are transferred upstream from the data conditioner 407 when aswitch 513 connects the data conditioner 407 to the digital opticaltransmitter 530.

The switch 513 is controlled by processor 550. When switch 513 is notconnected to the data conditioner 407, it can connect the output of theprocessor 550 to the digital optical transmitter 530. In other words,the switch 513 may be activated at appropriate times to combine theupstream RF packets from the data conditioner 407 with upstream datapackets from the processor 550 destined for the data service hub 110.More specifically, the RF packets may be inserted between upstreampackets comprising data generated by a subscriber with a communicationdevice such as a computer or telephone. The present invention is notlimited to a discrete switch 513 as described above. The switchfunctionality may be incorporated into the processor 550 or otherappropriate hardware device in the subscriber optical interface 140A.

Referring now to FIG. 7, this Figure is a functional block diagramillustrating a second subscriber optical interface 140B of an alternateembodiment that employs a single data stream and a phase locked loop523. Because of the similarities between FIGS. 6 and 7, only thedifferences between these two figures will be described.

A control word is loaded into the phase lock loop 523 to establish afrequency of the oscillator 526. In this embodiment, the localoscillator frequency can be determined by measuring the frequency of theincoming RF signal flowing out of a first low pass filter 519A. Themeasured frequency can be calculated by measuring the time between aplurality of zero crossings of the RF signal. Once the measuredfrequency is determined, then an offset frequency can be added to themeasured frequency such that the RF signal has side bands that extendnear, but do not cross, a zero frequency value.

The analog signal from the local oscillator 526 is mixed with the analogRF return signal generated by the video services terminal 117 in themixer 528 to produce a difference frequency. The difference frequency isfiltered with a second low pass filter 519B and is fed into an A/Dconverter 509. The difference frequency is converted to the digitaldomain with the A/D converter 509. The digital signals are then scaleddown with the data scaler 539 to reduce the amount of RF datatransmitted. The reduced digital signals are fed into the dataconditioner 407.

The data conditioner 407 at this stage, similar to the first exemplarysubscriber optical interface 140A discussed above, can speed up datatransmission of the digitized RF signals. The data conditioner 407 cancomprise a buffer such as a FIFO that also inputs identificationinformation with the digitized RF signals to form RF packets. Reduced RFsignals may enter the data conditioner 407 at an exemplary transmissionspeed of 40 Megabits per second (Mps) while the newly formed RF packetsexit the data conditioner 407 at an exemplary transmission speed of 500Megabits per second (Mps). However, other transmission speeds are notbeyond the scope of the present invention. RF packets are transferredupstream from the data conditioner 407 when a switch 513 connects thedata conditioner 407 to the digital optical transmitter 530, asdiscussed above similar to the first exemplary subscriber opticalinterface 140A.

Referring now to FIG. 8, this Figure is a graph 800 illustrating afrequency plan for the subscriber optical interface 140B of FIG. 7according to one exemplary embodiment of the present invention. Theupstream RF signal from the video services terminal 117 is extracted inthe first low pass filter 519A and supplied to the mixer 528. At themixer 528, the upstream RF signal is mixed with a carrier frequency(f_(C)) generated by the local oscillator 526. The mixer 528 producessum and difference frequencies from these two input signals as is wellunderstood by those skilled in the art. The difference frequency 805 isthe signal that will be digitized by the A/D converter 509. The sum orimage frequency 810 is not used and is eliminated by the second low passfilter 519B. The second low pass filter 519B can also eliminate anyother frequency component other than the difference frequency 805 thatis generated by the mixer 528. For example, the second low pass filter519B can eliminate the base RF signal produced by the video servicesterminal 117 and the carrier frequency (f_(C)) generated by the localoscillator 526. From the second low pass filter 519B, the differencefrequency 805 is fed into the A/D converter as discussed above withrespect to FIG. 7.

Referring now to FIG. 9, this Figure is a functional block diagramillustrating some components of a data-to-RF conversion block 307Aaccording to one preferred and exemplary embodiment of the presentinvention. This data-to-RF conversion block 307A is typically used inthe data service hub 110 when the first subscriber optical interface140A discussed above is used by the subscribers.

In this exemplary embodiment, the upstream RF packets are identified byeither an internet router 340 or the laser transceiver routing device355, depending on how the data service hub 110 is configured. The RFdata received from the router 340 or routing device 355 is restored witha scaling restoration unit 317. Further details of the scalingrestoration unit will be discussed below with respect to FIG. 19.

The restored RF packets are split into first and second data streamsafter the scaling restoration unit. At a first mixer 528A, the firstdata stream is mixed with the carrier frequency produced by the localoscillator 526. At a second mixer 528B, the second data stream is mixedwith a carrier signal produced by a phase shifter 527 that is ninetydegrees apart from a carrier frequency produced by a local oscillator526.

The first data stream and second data stream are then added together atan adder 905. The combined data stream is then converted back to theoriginal RF analog signal with a digital-to-analog (D/A) converter 910.The restored analog RF signal is then filtered with a bandpass filter915 and is then fed to RF receivers 309 connected to the video servicecontrollers 115.

Referring now to FIG. 10A, this figure is a functional block diagramillustrating some components of a second data-to-RF conversion block307B according to an alternate exemplary embodiment of the presentinvention. This second data-to-RF conversion block 307B is typicallyused in the data service hub 110 when the second subscriber opticalinterface 140B discussed above is used by the subscribers.

In this exemplary embodiment, the upstream RF packets are identified byeither an internet router 340 or the laser transceiver routing device,depending on how the data service hub 110 is configured. The upstream RFpackets are then used to reconstruct the original and fuller digitalsignal with the scaling restoration unit 317. Further details for thescaling restoration unit will be discussed below with respect to FIG.19.

During restoration, a control word for a phase locked loop 523 isdetermined. The control word for the PLL 523 is determined by measuringthe frequency of the incoming RF carrier frequency. This frequency maybe measured using any of several techniques known to those skilled inthe art. In one preferred and exemplary embodiment, the frequency ismeasured by counting the number of times the incoming RF carrier crosses0 volts during a predefined time interval. During this time interval thesubscriber video service terminal is transmitting a knownsynchronization word.

The control word is then loaded into the phase locked loop 523 to setthe frequency of a local oscillator 528. Meanwhile, the restored digitalRF signal is fed to a digital-to-analog converter 910 where it isconverted back into an analog RF signals.

The analog RF signal is filtered with a low pass filter 519. Thefiltered analog RF signal is then mixed with the carrier frequencyproduced by the local oscillator 526 at a mixer 528. The combined signalis then filtered by a bandpass filter 915.

Referring now to FIG. 10B, this figure is a graph 1000 illustrating afrequency plan for a data service hub 110 according to one exemplaryembodiment of the present invention. This frequency plan corresponds tothe signals produced by the second data-to-RF converter 307B illustratedin FIG. 10A.

Graph 1000 illustrates the response 1005 of the low pass filter 519 ofFIG. 10A. Graph 1000 also illustrates the signal 1010 produced by thelocal oscillator 526 and the image signal 1015. And lastly, Graph 1000further illustrates the response 1020 of the bandpass filter 915.

Referring now to FIG. 11, this Figure is a functional block illustratingexemplary components of another subscriber optical interface 140Caccording to an alternate exemplary embodiment of the present inventionthat can accommodate two RF return frequencies. In some legacy RF returnsystems, it is possible that two RF return frequencies will be used atdifferent times. Because both frequencies are typically not used at thesame time, sharing of hardware within a subscriber optical interface140C can be permitted to produce the RF return packets.

Because of the similarities between FIGS. 7 and 11, only the differencesbetween these two figures will be described. Operation of the embodimentillustrated in FIG. 11 is identical to that described above with respectto FIG. 7, however, the two outputs of the second low pass filters519B1, 519B2 are both supplied to the A/D converter 509. A signaldetector circuit 1105 is added to the second channel/frequency in orderto allow determination of which channel/frequency is active. This isnecessary in order to set the local oscillator 526 of the seconddata-to-RF converter 307B of FIG. 10A to the correct frequency.

Referring now to FIG. 12, this Figure is a logic flow diagramillustrating an exemplary method 1200 for propagating upstream RFsignals towards a data service hub 110. The description of the flowcharts in the this detailed description are represented largely in termsof processes and symbolic representations of operations by conventionalcomputer components, including a processing unit (a processor), memorystorage devices, connected display devices, and input devices.Furthermore, these processes and operations may utilize conventionaldiscrete hardware components or other computer components in aheterogeneous distributed computing environment, including remote fileservers, computer servers, and memory storage devices. Each of theseconventional distributed computing components can be accessible by theprocessor via a communication network.

The processes and operations performed below may include themanipulation of signals by a processor and the maintenance of thesesignals within data structures resident in one or more memory storagedevices. For the purposes of this discussion, a process is generallyconceived to be a sequence of computer-executed steps leading to adesired result. These steps usually require physical manipulations ofphysical quantities. Usually, though not necessarily, these quantitiestake the form of electrical, magnetic, or optical signals capable ofbeing stored, transferred, combined, compared, or otherwise manipulated.It is convention for those skilled in the art to refer torepresentations of these signals as bits, bytes, words, information,elements, symbols, characters, numbers, points, data, entries, objects,images, files, or the like. It should be kept in mind, however, thatthese and similar terms are associated with appropriate physicalquantities for computer operations, and that these terms are merelyconventional labels applied to physical quantities that exist within andduring operation of the computer.

It should also be understood that manipulations within the computer areoften referred to in terms such as creating, adding, calculating,comparing, moving, receiving, determining, identifying, populating,loading, executing, etc. that are often associated with manualoperations performed by a human operator. The operations describedherein can be machine operations performed in conjunction with variousinput provided by a human operator or user that interacts with thecomputer.

In addition, it should be understood that the programs, processes,methods, etc. described herein are not related or limited to anyparticular computer or apparatus. Rather, various types of generalpurpose machines may be used with the following process in accordancewith the teachings described herein.

The present invention may comprise a computer program or hardware or acombination thereof which embodies the functions described herein andillustrated in the appended flow charts. However, it should be apparentthat there could be many different ways of implementing the invention incomputer programming or hardware design, and the invention should not beconstrued as limited to any one set of computer program instructions.Further, a skilled programmer would be able to write such a computerprogram or identify the appropriate hardware circuits to implement thedisclosed invention without difficulty based on the flow charts andassociated description in the application text, for example. Therefore,disclosure of a particular set of program code instructions or detailedhardware devices is not considered necessary for an adequateunderstanding of how to make and use the invention. The inventivefunctionality of the claimed computer implemented processes will beexplained in more detail in the following description in conjunctionwith the remaining Figures illustrating other process flows.

Certain steps in the processes or process flow described below mustnaturally precede others for the present invention to function asdescribed. However, the present invention is not limited to the order ofthe steps described if such order or sequence does not alter thefunctionality of the present invention. That is, it is recognized thatsome steps may be performed before, after, or in parallel other stepswithout departing from the scope and spirit of the present invention.

Again, referring now to FIG. 12, this Figure provides an overview of theprocessing performed by the subscriber optical interfaces 140, lasertransceiver nodes 120, and data service hub 110. Step 1205 is the firststep in the exemplary upstream overview process 1200. In step 1205,terminal input is received at a video service terminal 117. Next, instep 1210, the terminal input is propagated as modulated analog RFsignals towards the subscriber optical interface 140.

In routine 1215, the analog RF signals are reduced and converted todigital packets. However, it is noted that routine 1215 does not need totake place in the subscriber optical interface 140. The reduction andanalog to digital conversion process can take place at the lasertransceiver node 120 or it could occur at the video service terminal117. Further details of routine 1215 will be described below withrespect to FIGS. 13 and 14.

In step 1220, identification information is added to the reduced RFpacket. This identification information can comprise headers used touniquely identify RF packets from other types of data packets. Theidentification information may further comprise a control word used byphase locked loops 523 during the scaling and restoration processesdescribed below. This identification information is typically suppliedby the data conditioner 407. However, the functions identified in step1220 can be accomplished with other hardware devices other than the dataconditioners 407. The present invention is not limited to the hardwaredevices which perform the functions described in step 1220.

In routine 1225, the reduced RF return packets are combined with regulardata packets. Further details of routine 1225 will be discussed belowwith respect to FIG. 16.

In step 1230, the combined electrical RF return packets and data packetsare converted to the optical domain at the subscriber optical interface140. Next, in step 1235, the combined optical packets are propagatedtowards the laser transceiver node 120 along a waveguide 150.

In step 1240, the combined optical packets are converted to theelectrical domain with a digital optical receiver such as the receiver370 of the laser transceiver node 120 as illustrated in FIG. 4. Thisconversion of the optical packets to the electrical domain in the lasertransceiver node 120 occurs because the laser transceiver node 120 iscombining data received from multiple groups of subscribers at theoptical tap routing device 435. Next, in step 1245, the reduced RFpackets are converted back to the optical domain by an optical waveguidetransceiver 430.

In step 1250, the reduced RF packets and the regular data packets arepropagated upstream towards a data service hub 110 along the opticalwave guide 170 that also carries down stream data packets that cancomprise telephone and data services. In step 1255 the reduced RFdigital packets and regular upstream data packets are converted back tothe electrical domain with the optical receivers 370 of the data servicehub 110.

In step 1260, the reduced RF packets are separated from the regularupstream data packets with either the internet router 340 or lasertransceiver node routing device 355 of the data service hub. In routine1265, the reduced RF packets are converted to the original RF analogsignals that were originally produced by the video service terminals117. Further details of routine 1265 will be described below withrespect to FIGS. 17 and 18. In step 1270, the RF analog signals arepropagated to the RF receiver 309 that is coupled to the video servicescontroller 115.

Referring now to FIG. 13, this Figure is a logic flow diagramcorresponding to the hardware of FIG. 6 and exemplary submethod 1215A ofFIG. 12 for reducing the size of the upstream RF signals and convertingthe analog RF signals to digital data packets according to one exemplaryembodiment of the present invention. Step 1305 is the first step of thesubmethod 1215A in which analog RF signals are filtered with the lowpass filter 519 of the diplexer 507 positioned in the subscriber opticalinterface 140A. In step 1310, the diplexer 507 passes the upstreamanalog RF signals to an analog-to-digital (A/D) converter 509.Meanwhile, in step 1315, the frequency of the phase locked loop 523 canbe determined by a frequency detector 521 that measures the frequency ofthe RF signal at the A/D converter 509 passing out of the low passfilter 519. The measured frequency can be calculated by measuring thetime between a plurality of zero crossings of the digitized RF signal.

In step 1320, the local oscillator 526 can be set to this measuredfrequency. Next, in step 1325, from the A/D converter 509, the digitalRF signals can be split into two data streams. In step 1330, a firstdata stream can be mixed down to a zero frequency in a first mixer 528Aby mixing the first data stream with a carrier frequency produced by alocal oscillator 526. In other words, this mixing process can be drivenby the local oscillator 526 which can be frequency controlled from aphase locked loop (PLL) 523.

In step 1335, a second data stream flowing out of the A/D converter 509can be mixed in a second mixer 528B with a carrier signal that is at thesame frequency as the first carrier or local oscillator signal, butphased ninety degrees apart from the first carrier signal. This phaseshift of the first carrier signal can be made with a phase shifter 527.

In step 1340, the first and second data streams flowing through thefirst and second mixers 528A, 528B can be propagated through low passfilters 519A, 519B. Next, in routine 1345, the two data streams can thenbe scaled down with a data scaler 539 in order to reduce the amount ofdigitized RF data transmitted. While in the data reducer 539, certainalgorithms are applied to reduce the amount of data transmitted. Anumber of algorithms related to subsampling and other techniques areknown to those skilled in the art. Further details of the data scaler539 and routine 1345 will be discussed below with respect to FIG. 15.

In step 1350, the two data streams are combined and muliplexed to a dataconditioner 407. The process then returns to step 1220 of FIG. 12.

Referring now to FIG. 14, this Figure is a logic flow diagramcorresponding to the hardware of FIG. 7 and exemplary submethod 1215B ofFIG. 12 for reducing the size of the upstream RF signals and convertingthe analog RF signals to digital data packets according to one alternateand exemplary embodiment of the present invention. Step 1410 is thefirst step of the exemplary submethod 1215B in which in which analog RFsignals from a video services terminal 117 are filtered with the lowpass filter 519 of the diplexer 507 positioned in the subscriber opticalinterface 140A.

Next, in step 1410, a control word for a phase locked loop 523 isdetermined. In step 1415, the control word is loaded into the phaselocked loop 523 to establish a frequency of the oscillator 526. In thisembodiment, the local oscillator frequency can be determined bymeasuring the frequency of the incoming RF signal flowing out of a firstlow pass filter 519A. The measured frequency can be calculated bymeasuring the time between a plurality of zero crossings of the RFsignal. Once the measured frequency is determined, then an offsetfrequency can be added to the measured frequency such that the RF signalhas side bands that extend near, but do not cross, a zero frequencyvalue.

In step 1420, the analog signal from the local oscillator 526 is mixedwith the analog RF return signal generated by the video servicesterminal 117 in the mixer 528 to produce a difference frequency. In step1425, the difference frequency is filtered with a second low pass filter519B and is fed into an A/D converter 509. Next, in step 1430, thedifference frequency is converted to the digital domain with the A/Dconverter 509. In routine 1435, the digital RF signals are then scaleddown with the data scaler 539 to reduce the amount of RF datatransmitted. Further details of the data scaler 539 and routine 1345will be discussed below with respect to FIG. 15. The process thenreturns to step 1220 of FIG. 12.

Referring now to FIG. 15, this Figure is a logic flow diagramillustrating an exemplary submethod 1345, 1435 of FIGS. 13 and 14 forscaling data received from a video service terminal 117 that can beperformed by a data scaler 539 as illustrated in FIGS. 8 and 9. The datascaling unit 539 removes unnecessary numbers of bits from each sample,while maintaining the maximum scaling of the data. The technique isfamiliar to those skilled in the art, and for example has been used inthe British NICAM (Near Instantaneous Compression and Modulation) methodof transmitting digital audio information on an analog channel.

FIG. 15 illustrates one exemplary data scaling algorithm 1345, 1435 thatcan be performed by data scaling unit 539. The data scaling algorithm1345, 1435 uses an example of reducing an 8 bit sample down to 4 bits,though other reductions can be used and are not beyond the scope of thepresent invention. The algorithm starts at step 1505. A counter, calledan MSB (most significant bit) counter is used in the routine to keeptrack of the number of places on the left of a data word have beeneliminated, as will be evident from the description below. The MSBcounter is initially set to a count of 0 in step 1510.

In step 1515, a block of data, such as, but not limited to, thirty-two8-bit bytes, are read and processed. Within that block of data, eachsample is examined in step 1520 to determine if the MSB is a 1 or a 0.If all samples in the block have a 0 in the MSB position, then theinquiry to decision step 1520 is answered “No”, meaning that the MSB isnot used in any data in that set of bytes. If the inquiry to decisionstep 1520 is negative, then the “No” branch is followed to step 1525 inwhich the data may be shifted left.

At the same time, the MSB counter referred to above is incremented by 1,to keep track of how many times the block has been shifted. Operationthen returns to decision step 1520, which again decides whether the MSBis used. If not, then the process repeats through step 1520, until theMSB is used. Note that this process applies to all the data words in theblock of data being processed.

When the MSB is used, then the inquiry to decision step 1520 is positiveand the “Yes” branch is followed to step 1530 in which the leastsignificant four bits of the word are dropped. Thus, the routine 1345,1435 has caused the retention of the four most significant bits thathave data, in the block of data. These bits are transmitted in step 1535along with the state of the MSB counter, which is used to reconstructthe waveform at the data service hub 110. The process then returns toeither to step 1350 of FIG. 13 or step 1220 of FIG. 12.

Referring now to FIG. 16, this Figure is a logic flow diagramillustrating an exemplary subprocess 1225 of FIG. 12 for combiningreduced RF packets with regular data packets. The combining reduced RFpackets with regular data packets routine 1225, starts with step 1605.In step 1605, the regular data transmission of ordinary data packetsproduced by the processor 550 in FIG. 8 is interrupted duringpredetermined intervals. As noted above, while the upstream transmissionof data packets can be interrupted at intervals with upstream RF packettransmission, it is noted that the intervals of interruption do not needto be regularly spaced from one another in time. However, in oneexemplary embodiment, the interruptions can be designed to be spaced atregular, uniform intervals from one another. In another exemplaryembodiment (not shown), the interruptions could be spaced at irregular,non-uniform intervals from one another.

In step 1610, reduced RF packets are inserted between irregular datapackets if the RF packets are available during an interval. Step 1610corresponds to the simultaneous activation of switches 513 in eachsubscriber optical interface 140 that is part of a subscriber grouping.The subscriber groupings are usually determined by the number ofsubscribers that will be serviced by a particular video service receiver309 that is typically located in the data service hub 110. After step1610, the subprocess ends and the process returns to step 1230 of FIG.12.

Referring now to FIG. 17, this Figure is a logic flow diagram thatcorresponds to the hardware of FIG. 9 and illustrates a preferredexemplary subprocess 1265A of FIG. 12 for converting reduced RF datapackets into original analog signals according to one exemplaryembodiment of the present invention. Routine 1705 is the first step ofthe subprocess 1265A in which the RF data packets received from eitherthe internet router 340 or laser transceiver node routing device 355 arerestored with the scaling restoration unit 317. Further details for thescaling restoration unit 317 and the scaling restoration routine 1705will be discussed below with respect to FIG. 19.

Next in step 1710, the upstream restored RF packets are divided intofirst and second data streams. Next, in step 1715, the first data streamis mixed with the carrier frequency produced by the local oscillator 526at the first mixer 528A. In step 1720, the second data stream is mixedwith a carrier signal produced by a phase shifter 527 that is ninetydegrees apart from a carrier frequency produced by a local oscillator526 at a second mixer 528B.

In step 1725, the first data stream and second data stream are thenadded together at an adder 905. In step 1730, the restored digital RFdata packets are then converted back to the original RF analog signalwith a digital-to-analog (D/A) converter 910. And in step 1735, therestored analog RF signal is then filtered with a bandpass filter 915.

Referring now to FIG. 18, this Figure is a logic flow diagram thatcorresponds to the hardware of FIG. 10A and that illustrates analternate exemplary subprocess 1265B of FIG. 12 for converting reducedRF data packets into original analog signals according to one exemplaryembodiment of the present invention.

Routine 1805 is the first step of the exemplary conversion subprocess1265B in which the original and fuller digital RF signal isreconstructed with the scaling restoration unit 317. Further details ofthe scaling restoration unit 317 and scaling restoration routine 1805will be discussed below with respect to FIG. 19.

During the restoration routine 1805, in step 1810, a control word for aphase locked loop 523 is determined. In other words, the control wordcan be read from the identification information of an upstream RF packetthat was produced by a data conditioner 407 in the subscriber opticalinterface 140, discussed above. Next, in step 1810, the control word isthen loaded into the phase locked loop 523 to set the frequency of alocal oscillator 528. Meanwhile, in step 1820, the restored digital RFsignal is fed to a digital-to-analog converter 910 where it is convertedback into an analog RF signals.

In step 1825, the analog RF signal is filtered with a low pass filter519. In step 1830, the filtered analog RF signal is then mixed with thecarrier frequency produced by the local oscillator 526 at a mixer 528.And in step 1835, the combined signal is then filtered by a bandpassfilter 915. The process then returns to step 1270 of FIG. 12.

Referring now to FIG. 19, this Figure illustrates an exemplary scalingrestoration process 1705, 1805 according to one exemplary embodiment ofthe present invention. The restoration process starts at step 1905. Thevalue of the MSB counter is read in step 1910, then data is read in1115. For each data word, the data is shifted right by the MSB countervalue in step 1920, with leading zeros being added to the left of thetransmitted bits. Of course, if fewer than the four most significantbits in the original word have been dropped, then some least significantbits are converted to zero by the process, but they represent only smallerrors in the recovered signal, and are tolerable.

In decision step 1925, it is determined whether all of the data thecurrent transmission or block has been read. If the inquiry to decisionstep 1925 is negative, then the “No” branch is followed back to step1915. If the inquiry to decision step 1925 is positive, then the “Yes”branch is followed to step 1930 where the data scaling restorationprocess ends and then returns to either step 1230 of FIG. 17 or step1810 of FIG. 18.

Referring now to FIG. 20, this Figure is a logic flow diagram thatcorresponds with the hardware of FIG. 11 and that illustratesmultiplexing to accommodate multiple RF return frequencies according toone alternate exemplary embodiment of the present invention. FIG. 20describes some actions taken by the data scaler 539 of FIG. 11 where itcontrols the phase locked loop 523 to “tune” either frequency/channel toa low frequency to be digitized by the A/D converter 509.

The data scaler 539 tunes to one frequency then to the other, pausinglong enough to determine if a signal is present at the A/D converter509. If a signal is not present at the A/D converter 509, then the datascaler tunes the phase locked loop 523 to the opposite frequency. Theexemplary multiplexing process 2000 begins with step 2005. This process2000 runs continually.

In step 2010, the data scaler 539 receives the first frequency, f1, froman element management system. An element management system (EMS) is acontrol system that interfaces with equipment to set up and changeoperating parameters and to receive, process, and display alarmsgenerated in the equipment. EMS's are generally well known to thoseskilled in the art. In step 2015, the data scaler 539 receives thesecond frequency, f2. These frequencies f1 and f2 can be suppliedmanually to the element management system. In Step 2020, the oscillator526 is set or tuned to frequency “f1.” The A/D converter 509 convertsany signal found into a digital signal. In Step 2025, a timer is set tozero.

In decision step 2030, the output of the A/D converter 509 is examinedto determine if a signal is present. In this step 2030, a signal ispresent if any of the second, third, or fourth bits from the leastsignificant bit (LSB) of the A/D converter 509 is one. If the second,third, or fourth LSB is one, then it is concluded that a signal ispresent, and the operation continues to step 2040 where data is gatheredfrom the A/D converter 509. After a block of data is gathered, in step2045, the data block is processed by the data reduction routine 1725,1805 of FIG. 19. After step 2045, in step 2050, the RF return data istransmitted to the data-to-RF converter 307 via processor 550 along withan indicator created by data conditioner 407 that frequency f1 wasconverted.

In decision step 2030, if the second, third, or fourth bit is not 1,then decision step 2030 yields a negative inquiry and the processproceeds to decision step 2035 in which it is determined whether thetimer has reached a time out. The timer is set to a time such that if asignal is present at the time that step 2025 is entered, then before thetimer times out, it will happen that the second, third, or fourth LSBwill have a non-zero value. This time may be computed from knowledge ofthe carrier frequency involved in the signal to be digitized and theamplitude that the set top communications system will drive the signalto. If the timer has not reached a time out (meaning that enough timehas not transpired for the second, third, or fourth bit to become one),then the process proceeds back to step 2030 and another sample is taken.

If in decision step 2035, the timer has timed out, and it is concludedthat frequency f1 is not present and the other frequency f2 should betested. The process proceeds to step 2055 in which the frequency f2 isexamined in a manner similar to f1 discussed above. In other words,steps 2060, 2065, 2070, 2075, 2080, and 2085 correspond with steps 2025,2030, 2035, 2040, 2045, and 2050.

Referring now to FIG. 21, this Figure is a logic flow diagramillustrating the exemplary processing 2100 of downstream video servicecontrol signals according to an exemplary embodiment of the presentinvention. The downstream process 2100 starts in first step 2105. Instep 2105, analog electrical video service control signals are receivedfrom a video service controller 115. Next, in step 2110, the analogelectrical video service control signals are combined with analogdownstream video signals.

In step 2115, the analog electrical video service control signals andvideo signals are converted to the optical domain with an opticaltransmitter 325. The combined video optical signals are propagatedtowards laser transceiver nodes 120 via optical wave guides 160. In step2125, the combined video optical signals are also combined with dataoptical signals in the laser transceiver node 120. Specifically, in anexemplary embodiment of the present invention, the video optical signalscan be combined with the data optical signals in a diplexer 420.

The combined video and data optical signals are propagated along anoptical wave guide 150 to a subscriber optical interface 120. In step2135, the video optical signals are separated from the data opticalsignals with an optical diplexer 515. The video optical signals are thenconverted to the electrical domain with an analog optical receiver 525.

In step 2145, the video service control signals are separated from theregular video signals in the video services terminal 117. Next, in step2150, the video service control signals are processed by the videoservice terminal 117.

Alternate Embodiments

The present invention is not limited to the aforementioned lasertransceiver nodes 120. The present invention may employ nodes 120 thatoperate with LEDs that produce wavelengths that may be unique tosubscribers or groups of subscribers. In other words, each node 120 canfurther comprise one or more wavelength division multiplexers anddemultiplexers. Each wavelength division multiplexer (WDM) can selectone or more wavelengths of optical bandwidth originating from arespective optical tap multiplexer. Each WDM can then combine the one ormore wavelengths of optical bandwidth together and feed them into asingle optical waveguide 150. In this way, one optical waveguide 150 canservice a number of individual optical taps 130 that can correspond tothe number of optical tap multiplexers 440 present in the bandwidthtransforming node 120. In such an exemplary embodiment, each optical tap130 can divide data signals between a plurality of subscribers and canbe capable of managing optical signals of multiple wavelengths.

The present invention is not limited to providing a return path for justlegacy video service terminals 117. The return path of the presentinvention can be carry signals of other hardware devices that may notcharacterized as “legacy” hardware.

The present invention may simply be used to provide increased bandwidthfor additional conventional electronic communication devices that aresupported by the optical network.

CONCLUSION

Thus, the present invention provides a unique method for inserting RFpackets (derived from RF signals produced by a video service terminal)between upstream packets comprising data generated by a subscriber witha digital communication device such as a computer or internet telephone.Thus, the present invention provides an RF return path for legacyterminals that shares a return path for regular data packets in anoptical network architecture.

It should be understood that the foregoing relates only to illustratethe embodiments of the present invention, and that numerous changes maybe made therein without departing from the scope and spirit of theinvention as defined by the following claims.

1. A return path of an optical network system comprising: a data servicehub for generating downstream optical signals and for transmittingdownstream RF-modulated video service control signals, and for receivingupstream RF-modulated video service control signals that are propagatedthrough the optical network system according to one of a contentionnetwork protocol and a query-response protocol, the contention networkprotocol and query-response protocol supporting the control signalsindependently of time, the data service hub comprising a data scalingrestoration unit for restoring upstream RF-modulated video servicecontrol signals into an original format; and at least one subscriberoptical interface coupled to the data service hub for receiving thedownstream optical signals, and for receiving RF-modulated signalscomprising upstream video service control information that is propagatedaccording to one of the contention network protocol and thequery-response protocol, the subscriber optical interface comprising anA/D converter for converting the RF-modulated signals to digitalsignals, the subscriber optical interface comprising a data scaling unitfor reducing data contained within the digital signals, the subscriberoptical interface modulating an optical carrier with the digital signalsfor generating upstream optical signals according to a timing dependentprotocol and which are sent to the data service hub.
 2. The return pathof claim 1, wherein the data service hub comprises a video servicecontrol terminal for transmitting downstream RF-modulated video servicecontrol signals.
 3. The return path of claim 1, wherein the subscriberoptical interface converts the digital signals to digital packets. 4.The return path of claim 3, wherein the digital packets are firstdigital packets, the subscriber optical interface combining the firstdigital packets with second digital packets in the time domain andaccording to the timing dependent protocol for upstream transmission ofthe combined first and second packets.
 5. The return path of claim 1,further comprising one or more optical waveguides connected to thesubscriber optical interface, for carrying the upstream optical signalsand downstream optical signals.
 6. The return path of claim 1, furthercomprising a laser transceiver node for communicating optical signals tothe data service hub, and for apportioning bandwidth between subscribersof the optical network system.
 7. The return path of claim 4, whereinthe second packets comprise data other than the RF-modulated videoservice control signals.
 8. A method for providing a return path forRF-modulated video service signals in an optical network systemcomprising the steps of: receiving one or more RF-modulated videoservice control signals comprising upstream control informationpropagated through the optical network system according to one of acontention network protocol and a query-response protocol, thecontention network protocol and query-response protocol supporting thecontrol information independently of time; converting the one or moreRF-modulated video service control signals to digital signals with anA/D converter; reducing data contained within the digital signals with adata scaling unit; propagating the digital signals towards a dataservice hub on an optical carrier over the optical network systemaccording to a timing dependent protocol; receiving the digital signalsat the data service hub; and converting the digital signals with acontrol terminal comprising a data scaling restoration unit back into anoriginal format, the original format comprising the RF-modulated videoservice control signals that comprise control information propagatedaccording to one of the contention network protocol and thequery-response protocol.
 9. The method of claim 8, further comprisingconverting the digital signals to first digital information packets, andreceiving a plurality of second digital information packets.
 10. Themethod of claim 9, further comprising transmitting the first and seconddigital information packets by inserting the first digital informationpacket between the second digital information packets during a timeinterval.
 11. A method for returning RF signals to a data service hubcomprising: receiving modulated analog RF video service control signalsat a subscriber optical interface comprising upstream video servicecontrol signals propagated according to one of a contention networkprotocol and a query-response protocol, the contention network protocoland query-response protocol supporting the video service control signalsindependently of time; converting the analog RF video service controlsignals into digital RF signals; reducing the amount of data containedin the digital RF signals with a data scaling unit; converting thedigital RF signals into one or more packets; propagating the packetstowards the data service hub with an optical carrier according to atiming dependent protocol; receiving the packets at the data servicehub; converting the packets into digital RF signals; and converting thedigital RF signals with a control terminal comprising a data scalingrestoration unit back into an original format, the original formatcomprising the RF video service control signals that comprise controlinformation propagated according to one of the contention networkprotocol and the query-response protocol.
 12. The method of claim 11,wherein the one or more packets are first packets, the method furthercomprising receiving a plurality of second packets comprisinginformation different from the control signals.
 13. The method of claim12, further comprising combining the one or more first packets with thesecond packets during a time interval.
 14. The method of claim 11,further comprising converting the packets at the data service hub backinto the analog RF signals with a control terminal, the analog RFsignals preserving one of the contention network protocol and thequery-response protocol.
 15. The method of claim 12, wherein the secondpackets comprise at least one of data generated by a computer and datagenerated by a telephone.
 16. The method of claim 12, wherein the firstand second packets comprise Ethernet packets.